1. Field of the Invention
The present invention relates to a liquid crystal display device used for a monitor of, for example, computers, wordprocessors, car navigation systems, and TVs, and a method for producing the same.
2. Description of the Related Art
Today, TN (twisted nematic) liquid crystal display devices (hereinafter, referred to as “LCD devices”) are in wide use. In a TN LCD device, upper and lower alignment layers are treated by rubbing in different direction from each other, so that liquid crystal molecules are in a twisted alignment in the state where no voltage is applied. The TN LCD device has problems of a gray scale inversion phenomenon and an excessive dependency of the display quality on the viewing angle.
In order to solve such problems, a liquid crystal material having a negative dielectric anisotropy and a vertical alignment mode which uses a vertical alignment layer has been proposed. The vertical alignment mode provides a black display when no voltage is applied. A satisfactory black display is obtained in a quite large viewing angle range by using, for example, a phase plate having a negative refractive index anisotropy. The use of such a phase plate substantially compensates for birefringence caused by a liquid crystal layer in which the liquid crystal molecules are vertically aligned when no voltage is applied. In this manner, a high contrast display is realized in a wide viewing angle range. However, the vertical alignment mode has a problem of a gray scale inversion phenomenon which is observed in a direction identical with the direction in which the liquid crystal molecules are tilted when a voltage is applied.
Japanese Laid-Open Publication No. 6-301036 discloses an LCD device having an opening at a center of an area of a counter electrode, the area corresponding to a pixel electrode. Such a structure causes an electric field between the pixel electrode and the counter electrode to be inclined with respect to surfaces thereof, whereas the electric field is vertical with respect to the surfaces without such a structure. Accordingly, when a voltage is applied in the vertical alignment mode, the liquid crystal molecules are tilted in an axially symmetrical manner. The dependency of the display quality on the viewing angle of such an LCD device is averaged in all azimuth directions when compared with an LCD device in which the liquid crystal molecules are tilted in one direction. As a result, the LCD device disclosed in the above-mentioned publication provides a quite satisfactory viewing angle characteristic.
Japanese Laid-Open Publication No. 8-341590 discloses an LCD device having a projection surrounding a pixel region or divided pixel region and also an alignment fixing layer. Such a structure defines the position and the size of the liquid crystal region in which the liquid crystal molecules are aligned in an axially symmetrical manner, and stabilizes the axially symmetric alignment of the liquid crystal molecules.
However, the structure disclosed in Japanese Laid-Open Publication No. 6-301036 makes it difficult to generate an electric field inclined with respect to the electrode surface uniformly in the entirety of pixel regions. As a result, the liquid crystal molecules respond to the application of the voltage in a delayed manner in a part of the pixel regions, which results in an image sticking phenomenon.
The structure disclosed in Japanese Laid-Open Publication No. 8-341590 requires a projection to be formed of a resist or the like on a base plate. This increases the number of production steps and thus raises the cost.